newtons laws of motion

Question 1

what is newtons first law

Answer 1

objects either stay at rest or move with constant velocity unless acted on by a force

Question 2

an object moving at constant velocity is either …

Answer 2

acted on by no forces or the forces acting on it are balanced (so the resultant force is zero)

Question 3

acceleration is always in the same direction as the …

Answer 3

resultant force

Question 4

what is newtons second law

Answer 4

states that the net force acting on an object is equal to the rate change of momentum it experiences.
F=p/t
F=mv/t
F=m x v/t
F=ma

Question 5

what does newtons second law tell us about what shappening to the object

Answer 5

object is experiencing change in momentum
object is experiencing change in velocity, speed ,direction or acceleration
there must be net force acting on object

Question 6

why do heavier objects fall at the same rate as lighter objects

Answer 6

because for a mass in free fall
acceleration=the force of gravity mg / mass m
=g
therefore the rate at which objects fall is independent the rate of m

Question 7

A vehicle of mass 600 kg accelerates uniformly from rest to a velocity of 8.0ms^-1 in 20s. Calculate rhe force needed to produce this acceleration.

Answer 7

a=v-u/t
a=8-0/20
a=0.4ms^-2
F=ma
F=600x0.4
F=240N

Question 8

the measure of g depends on its …

Answer 8

location/planet

Question 9

the mass of an object is a measure of its …

Answer 9

inertia which is its resistance to change of motion

Question 10

how to find the acceleration of object acted on by two opposite forces

Answer 10

F1-F2=ma

Question 11

how to work out the resultant force or car towing trailer

Answer 11

F-T=Ma
T=ma
F=Ma + ma

Question 12

what equation d you use when working on rocket problems

Answer 12

T=mg + ma
T(thrust)

Question 13

what equation do you use when lift is moving at constant velocity

Answer 13

T=mg
T(tension)

Question 14

what equation do you use if lift is moving up and accelerating

Answer 14

T=mg + ma
T-mg=ma

Question 15

what equation do you use if a lift is moving and down accelerating

Answer 15

mg = ma + T
mg-T=ma

Question 16

how do you approach pulley problems

Answer 16

work out equation for both masses using
T-mg=ma &
Mg-T=Ma
and then do simultaneous equations

Question 17

what does drag force depend on in a fluid

Answer 17

shape of object
its speed
the viscosity of liquid (how easily an fluid flows past a surface)

Question 18

what is terminal speed

Answer 18

maximum speed a object can reach when all the forces are balanced

Question 19

what is needed for terminal speed to be reached when an object falls

Answer 19

drag force has to be equal and opposite to the objects weight so its acceleration is zero and so its speed remains constant when it falls

Question 20

how do you work out the resistive force

Answer 20

by adding all the drag forces acting on the object

Question 21

what is the resultant force of a objet when resistive forces act on it

Answer 21

F(motive)-F(resistive)=ma

Question 22

what is thinking distance

Answer 22

distance travelled in the time it takes to react

Question 23

what is braking distance

Answer 23

distance travelled by a car in the time it takes to stop safely from when brakes are first applied

Question 24

stopping distance

Answer 24

thinking distance + braking distance

Question 25

A car can only move forwards by pushing ... on the road

Answer 25

backwards

Question 26

When you push ... on the ground, the ground exerts an equal and opposite force on you that enables you to move forward.

Answer 26

backwards

Question 27

braking distance depends on ...

Answer 27

the speed of the vehicle the instant the brakes are applied

Question 28

on an icy or greasy road skidding is more likely because

Answer 28

the limiting frictional force between the road and the tyres is reduced from its dry value

Question 29

what is newtons third law

Answer 29

for every force acting on an object, the object will exert an equal and opposite force on its cause